Routing switchers

What could be simpler than taking a unidirectional signal in and passing it on unchanged?
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NVISION'S NV8256-plus router

What could be simpler than taking a unidirectional signal in and passing it on unchanged? How can something so fundamentally uncomplex be so important to our industry? The answer lies in the complexity that is under the covers.

The routing switcher began life as a simple crossbar switcher, much like a telephone switch. Many inputs could be connected to many outputs but, unlike a telephone switch, one input could be replicated to all outputs at the same time, a kind of super-flexible distribution amplifier. Early incarnations were usually two switchers under strict parallel control, with one audio level and one video level married together on a one-for-one basis. Breakaway was possible, but without the ability to map crosspoints to logical pairings like we see today.

As time passed, it became clear that the switcher needed more capability. Signal paths became much cleaner as the requirement to circle through the system many times became increasingly important. Stereo audio levels were added, as were machine control functionality, RS-422 matrices, tally, and sophisticated control systems that allowed multiple levels for key signals and other functions. Input mapping became virtual, allowing system reconfiguration without rewiring a plant around one piece of equipment. Reliability increased, and one manufacturer offered a 10-year warranty. (And still does!) Control systems went from embedded real-time systems to reprogrammable software systems with redundant processors.

Today, all of this seems like the dark ages. Routing has taken such a key position in mission-critical operations that some manufacturers have taken a fresh look at how to best protect their clients. Careful planning for eventual failure once enhanced reliability. For instance, signals were disbursed among physical I/O cards to ensure that one random board failure could not take all inputs to the MCR off the air. While this strategy is quite effective, as blocks of crosspoints have climbed from 10×10 to as high as 128×128, it is no longer practical to “work around” a significant failure. Both NVISION and Utah Scientific have developed internal redundant cards that can seamlessly replace crosspoints and I/Os. Utah Scientific has built-in signal presence detection that can allow the control system to sense a lost input and automatically replace it with an alternate signal, a copy of the main signal or a suitable replacement. NVISION put a redundant crosspoint into the frame that allows for potential failure of a large block of crosspoints and their replacement, with no effect on any output.

Control systems are embracing TCP/IP for distribution of control to panels and for communication to other devices. This facilitates some of the more important changes. Web-based monitoring and configuration has begun to be a valuable and simple way to interact with control systems. NVISION, with its Envy control system, has pioneered a new Web interface — featured in products from Thomson Grass Valley, Utah Scientific and others — that permits more flexible maintenance and operational features. Remote monitoring and diagnosis can now be done from anywhere, including from a manufacturer's plant. As systems become more complex, and labor budgets get even tighter, this will increasingly be a valuable tool.

This movement to IP control also facilitates wide-area connection of virtual control systems. The European Broadcasting Union, has connected a Thomson Grass Valley Encore control system between Washington and New York, with software control panels distributed in 10 cities across Europe over private data bandwidth. Though not for the faint of heart, the same thing could be done using VPN connections over the public network for temporary or low usage control.

Control panels are becoming highly configurable. With programmable button legends being offered, it is not hard to see how the entire button set can be flexible, allowing buttons to be assigned to special purpose functions or macros.

The contents of a router frame remained remarkably the same until recently. For many years, stereo audio routing switchers have been capable of channel summing or track reversal. A few years ago, wide bandwidth routing became available. The ability to mix HDTV signals with digital 525/625 signals was an important change. But this year, a more important evolution occurred. Several manufacturers now offer analog-to-digital conversion (and the reverse) for audio and video signals. In some cases, these are special purpose I/O cards. In the case of the Thomson Grass Valley Concerto audio router, the standard audio cards (analog and digital) can be mixed in one frame, allowing flexible I/O with internal conversion both directions.

But more exciting is the inclusion by Quartz and others of new functionality in routing. Keyers have shown up in Quartz's Xenon router. It is easy to see how a routing switcher could become a simple master control switcher. For DTV multiplex this is particularly appealing. It is easy to feed all the signals to one box and take out combined or individual signals. Functionality could be distributed via IP if a few other simple features were added, such as a simple mix multipler with key and 2-D squeeze, full-featured master control, or a small production control room. Install a virtual monitor wall processor, a VGA level to the router, and voil, you have instant control rooms. With streaming processors like H.264, a control room could be located anywhere, with the router acting as an intelligent signal processor on a grand scale.

John Luff is senior vice president of business development for AZCAR.

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